1. Field of the Invention
This invention pertains to optical transmission systems. In particular it refers to single reflective mirror transmission systems which use a reflective surface to focus the light source into a predetermined pattern.
2. Description of the Prior Art
A mirror of unconventional optical design has been used for some years as the principal optical component of a passive infrared target detector. The practical experience gained through the use of this optical design concept and passive receiver generated the high level of confidence in the variations inherited in the design geometry. Beyond the configuration used in passive receivers, little documented evidence existed in support of design potential for other applications. The original studies performed led to the concept of the bullet mirror. The bullet mirror provided a way of funneling light from given sources into a modified output beam.
Limitations of the bullet mirror were principally the following:
1. The interaction of the laser diode and the bullet mirror was shown analytically and experimentally to affect a reduced efficiency from vignetting of the laser diode light emissions imposed by the alignment geometry required to achieve the necessary azimuthal coverage in the projected light beam.
2. The bullet mirror could not fully collect the laser diode emissions and maintain the required azimuthal coverage in the projected conical sector of light.
3. The inconsistancies from one laser diode to another in their raw light emission spatial characterictics appears to introduce considerable alignment problems. The difficulties observed with the laser diodes seemed to be resolvable only by a tedious sorting of diodes.
These numerated difficulties and others were sufficient to justify new ideas for the transmitter design. Modifying the mirror itself appeared to be more profitable than modifying the laser diode. In an effort to extend the basic concept of the single reflecting transmitter, innovations in the bullet mirror concept were addressed.
A modified paraboloidal mirror was seen to be analytically possible in that it would overcome the deficiencies of the earlier bullet mirror transmitter designs. The modified mirror would retain the basic beam shaping properties that had been demonstrated feasible with a single mirror. The paraboloidal transmitter was shown analytically to have considerably improved performance capabilities when the focal distance was made a function of the angle measured around the axis of revolution. This modified surface is the wavy mirror.